Age-dependent influence of heart rate on Doppler indexes of left ventricular filling

Abstract. Background and objective . The Doppler indexes of left ventricular filling are related to age and heart rate. The aim of this study was to assess whether the influences of heart rate and age interactions (that is, whether the effect of heart rate on the Doppler indexes) is modified by age. Subjects and methods . The effects of atropine-induced heart rate increases on the transmitral velocities were compared in 10 younger healthy subjects aged 26–38 years and 12 older healthy subjects aged 50–67 years. Results . With a comparable total rise in heart rate (on average 20 beats min^-1), the peak early diastolic velocity decreased likewise in both groups (from 66±9 to 57±9 cm s^-1 in the younger age group and from 58 ± 15 to 47±13 cm s^-1 in the older age group). The peak atrial velocity remained unaltered in the older group (53 ± 16 vs. 52 ± 14 cm s^-1) but rose from 33 ± 6 to 44 ± 12 cm s^-1 in the younger (P = 0.02). The early-to-atrial peak velocity ratio decreased from 1.2 ± 0.6 to 1.0 ± 0.4 cm s^-1 in the older subjects and from 2.0 ± 0.5 to 1.4 ± 0.5 cm s^-1 in the younger subjects (P = 0.01). Changes in the other Doppler indexes were similar in both groups. Conclusions . The effect of heart rate on certain Doppler indexes of left ventricular filling is age-dependent. The peak velocity ratio cannot be interpreted without adjusting for heart rate in younger subjects, whilst in older people heart rate variation is of less importance.     

102名健康中年人运动试验前后舒张功能的正常变异

目的：观察健康中年人运动试验前后舒张功能的变化。方法：使用多普勒彩色超声心动图仪分别测量102名健康中年人静息时、运动试验后15min及60min的E峰最大流速（EPFV）、A峰最大流速（APFV）、EPFV／APFV（EK／A）比值、E峰减速时间（Edt)。结果：健康中年人运动试验后15min及60min EPFV、E／A比值、Edt与静息时相比均明显下降。APFV运动试验前后无差异。运动试验后15min E/A比值比静息时降低0．5以内。结论：健康中年人运动试验后舒张功能存在生理性下降，运动后15min的E／A比值较静息时明显降低，但应＜0．5。     

102名健康中年人运动试验前后舒张功能的正常变异

目的观察健康中年人运动试验前后舒张功能的变化.方法使用多普勒彩色超声心动图仪分别测量102名健康中年人静息时、运动试验后15min及60min的E峰最大流速(EPFV)、A峰最大流速(APFV)、EPFV/APFV(E/A)比值、E峰减速时间(Edt). 结果健康中年人运动试验后15min及60min EPFV、E/A比值、Edt与静息时相比均明显下降.APFV运动试验前后无差异.运动试验后15min E/A比值比静息时降低0.5以内. 结论健康中年人运动试验后舒张功能存在生理性下降,运动后15min的E/A比值较静息时明显降低,但应＜0.5.     

Intrinsic left ventricular contractility in normal subjects

The influence of autonomic tone on left ventricular (LV) contractility, along with the range of normal values and the effects of exercise on contractile state, were studied in 12 normal volunteers. Serial reproducibility was examined in a subgroup of 6. LV contractility was estimated by the LV peak-systolic pressure to end-systolic volume relation (pressure-volume relation), and the ratio of peak-systolic pressure to end-systolic volume (pressure/volume ratio). The cuff blood pressure and radionuclide ventriculogram were recorded at rest, during exercise and during pharmacologic pressure-afterloading with phenylephrine, before and after vagal and beta-adrenergic "blockade." Both the pressure/volume ratio and ejection fraction increased during the stimulus of exercise (both p less than or equal to 0.008). After blockade, the pressure-volume relations were highly linear (r = 0.95 +/- 0.05 [standard deviation], n = 12), and there was no systematic difference in their slopes induced by blockade. The serial studies of pressure-volume relations showed no significant differences. The results demonstrated that vagal and sympathetic tone were not important in the support of LV contractility in normal subjects at rest, and that the pressure-volume relation and pressure/volume ratio are reproducible between studies. Also, the findings confirmed that both the pressure/volume ratio and the ejection fraction were sensitive to exercise-induced changes in contractility. This demonstration of intrinsic LV contractility in normal subjects, plus the reproducibility of the measurements, supports the feasibility of serial study of LV contractility.     

Effect of left ventricular wall mass on Doppler filling patterns in the developing normal human heart

To assess gestational age- and growth-related changes in left ventricular (LV) size, LV wall, and LV transmitral flow velocity patterns, 2-dimensional (2-D) and Doppler echocardiographic studies were performed in 89 normal fetuses aged 16 to 38 weeks. Serial studies were designed in 7 fetuses. Variables measured from 4-chamber views were chamber areas and myocardial wall areas. From these measurements, area shortening fraction and ratio of myocardial wall area to end-diastolic chamber area were calculated. LV end-diastolic chamber area and myocardial wall area increased exponentially with advancing gestational age (r = 0.88 and 0.90, respectively, p < 0.001). Area shortening fraction showed no significant changes with gestational age. Ratio of myocardial wall area to LV end-diastolic chamber area decreased gradually with increasing gestational age (r = -0.77, p < 0.001). With increasing gestational age, mitral peak velocities of early diastole increased (r = 0.82, p < 0.01) with little change in peak velocity during atrial contraction. Multiple regression analysis showed that age-related increases in peak velocity of early diastole were related to advancing gestational age and also to decreases in ratio of myocardial wall area to LV end-diastolic chamber area. Low peak filling velocities during early diastole in younger fetuses may be related partly to relative increase in LV wall mass. The gestational age-related decreases in LV wall mass may be one of the important mechanisms of gestational age-related alterations in diastolic properties, especially relaxation processes.     

Twenty-four-hour heart rate and blood pressure are additive markers of left ventricular mass in hypertensive subjects

BACKGROUND: We investigated whether mean heart rate (HR(24)) and blood pressure (BP) parameters during 24-h ambulatory BP monitoring (ABP) are independent or additive markers of left ventricular (LV) mass in subjects with newly diagnosed, untreated hypertension. METHODS: A total of 250 patients (40% women, 60% men; mean age 59.6 +/- 11 years) with essential hypertension who were attending the outpatient Hypertension Unit were studied. All patients underwent 24-h ABP and HR monitoring as well as echocardiography for assessment of left ventricular (LV) dimensions and function. RESULTS: A decreasing HR24 or increasing ABP parameters (ie, systolic, diastolic, mean BP, and pulse pressure) were associated with increasing LV mass (P < .001) and wall thickness (P < .01). In multivariate analysis, after adjusting for age, gender, body surface area, body mass index, hematocrit, glucose, cholesterol, smoking, and each of the measured ABP parameters separately, decreasing HR24 was independently related to increasing LV mass in addition to ABP and body size parameters (P < .001). The addition of HR24 in different multivariate models for prediction of LV mass significantly increased the adjusted model r2 (range of r2 change: 0.039 to 0.064, P for change <.05). Decreasing HR24 or HR during daytime (6 am to 10 pm) was associated with a higher likelihood of LV hypertrophy in addition to ABP parameters (adjusted odds ratio 0.92 (CI 0.87 to 0.98), per 1 beat/min greater HR24 P = .002 and 0.93 (CI: 0.87 to 0.98), per 1 beat/min greater HR in the daytime P = .017). CONCLUSION: The 24-h HR and BP during ABP are independent and additive markers of increased LV mass in untreated hypertensive individuals.     

Effect of loading conditions, contractile state, and heart rate on early diastolic left ventricular filling in conscious dogs.

We investigated left ventricular (LV) early diastolic filling in 10 normal conscious dogs that had been previously instrumented to measure LV and left atrial (LA) pressures and three orthogonal LV internal dimensions. LV volume was calculated as a general ellipsoid. The pressure within a passive structure increases as it is filled. If myocardial relaxation is rapid enough to substantially aid LV diastolic filling, it may overcome this effect and cause LV pressure to fall despite an increase in volume. Thus, we defined the amount of LV filling that occurred while LV pressure was falling as relaxation filling, which is a measure of the importance of LV relaxation during early diastolic filling. The time constant of relaxation (T) was derived from the exponential fall of LV pressure during isovolumic relaxation. While LV pressure was falling early in diastole (the relaxation filling period), all three LV diameters increased. Autonomic blockade with hexamethonium (5 mg/kg) and atropine (0.1 mg/kg) reduced relaxation filling from 21 +/- 6% (mean +/- SD) to 12 +/- 3% of the stroke volume (p less than 0.01). The mean LA pressure also was significantly decreased (from 12 +/- 2 to 10 +/- 5 mm Hg, p less than 0.05), while the duration of the relaxation filling period and T were unchanged. Positive inotropic stimulation with dobutamine (10 micrograms/kg/min) shortened T without changing LA pressure. The maximum LA-LV pressure gradient, dV/dtmax, and relaxation filling all increased. Augmented preload produced by dextran infusion (500 ml/10 min) caused an increase in LA pressure (from 11 +/- 3 to 21 +/- 8 mm Hg, p less than 0.05) without altering T. This also increased the maximum LA-LV pressure gradient, dV/dtmax, and relaxation filling. Augmented afterload produced by methoxamine (10 mg/3 min i.v.) significantly increased LA pressure (from 9 +/- 4 to 15 +/- 10 mm Hg, p less than 0.05) and lengthened T (from 35 +/- 4 to 50 +/- 7 msec, p less than 0.05) and the duration of relaxation filling (from 36 +/- 5 to 44 +/- 9 msec, p less than 0.01) without altering the maximum LA-LV pressure gradient, dV/dtmax, or LV relaxation filling. Incremental changes in heart rate induced by atrial pacing (from 100-180 beats/min) resulted in progressive decreases in the time constant of LV relaxation and the duration of relaxation filling. The LA pressure was also decreased. There was no corresponding increase in the amount of active LV filling until the heart rate reached 180 beats/min. During all these interventions, T correlated with the duration of LV relaxation filling (r = 0.99. p less than 0.05). The amount of relaxation filling and dV/dtmax both correlated with the maximum LA-LV pressure gradient.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of acute alterations in left ventricular loading conditions on peak filling rate in the denervated (transplanted) ventricle

Peak filling rate is an indicator of left ventricular (LV) diastolic function. It is influenced by heart rate, loading conditions, sympathetic nervous system activity, ejection fraction and other factors. To determine the effect of altered loading conditions on peak filling rate, independent of heart rate and sympathetic nervous system activity, 12 patients were studied 3 weeks after orthotopic heart transplantation. Plasma catecholamine level, heart rate and ejection fraction were not changed by any maneuver. Nitroglycerin caused a decrease in pulmonary artery wedge pressure (9 +/- 2 to 6 +/- 1 mm Hg, p less than 0.001) and in absolute peak filling rate (46.0 +/- 3.0 to 42.8 +/- 2.5 kcts/s, p less than 0.01), but no change in normalized peak filling rate. Volume infusion increased pulmonary artery wedge pressure (9 +/- 2 to 12 +/- 2 mm Hg, p less than 0.001) and absolute peak filling rate (46.0 +/- 3.0 to 51.5 +/- 5.3 kcts/s, p less than 0.01), but peak filling rate normalized to stroke volume was unchanged. During nitroglycerin and volume infusions, there was a high correlation between changes in pulmonary artery wedge pressure and absolute peak filling rate (r = 0.82, p less than 0.001). With normalization of peak filling rate, these variables correlated less well. With methoxamine, 4 patients demonstrating systolic dysfunction had a decrease in absolute and normalized peak filling rate despite a large increase in pulmonary artery wedge pressure. The other 8 patients without systolic dysfunction had an increase in pulmonary artery wedge pressure with increased absolute but unchanged normalized peak filling rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Factors influencing Doppler indexes of left ventricular filling in healthy persons

Ninety-three healthy persons aged 11 to 91 years were studied to assess the factors influencing Doppler indexes of left ventricular (LV) diastolic filling. The effects of physical activity, alcohol consumption and smoking were tested in addition to those of age, sex, heart rate, body mass index, blood pressure, left atrial diameter, and LV end-diastolic diameter, wall thickness, mass and fractional shortening. The data were fitted stepwise into multiple linear regression models both in the total population and in 3 groups aged less than 40, 40 to 60 and greater than 60 years. In the total population, age explained 45 to 68% of the variation in the peak early and late diastolic velocities, their ratio, deceleration of the early velocity, atrial filling fraction and peak filling rate normalized to mitral stroke volume. With advancing age--and with increases in either body mass index, heart rate, diastolic blood pressure or LV mass--the indexes of early filling decreased, whereas with regular modest use of alcohol or regular aerobic exercise they increased (p less than 0.05 for all). In the middle-aged subjects, gender explained 32 to 57% of the variation in the peak atrial velocity, early to atrial peak velocity ratio and atrial filling fraction; the peak velocity ratio measured 1.4 +/- 0.3 (mean +/- standard deviation) in men vs 1.0 +/- 0.2 in women (p less than 0.001). In conclusion, many constitutional and physiologic factors and even life-style can influence the Doppler indexes of LV filling. This demonstrates the exquisite sensitivity of the method but indicates also that individual measurements must be interpreted with caution.     

Relationship of Doppler indexes of left ventricular filling and exertion tolerance]

The aim of this study was to evaluate if Doppler indexes of left ventricular filling are related to exercise capacity. Since a correlation between left ventricular filling pattern and causal blood pressure has been recently reported along a wide range of pressure values, a group of subjects with blood pressure ranging from normal to severely elevated values was studied. Twenty-four subjects (11 normotensives, 13 mild to severe hypertensive patients) underwent an echo-Doppler study and a maximal multistage cycloergometric exercise test. Since the cycloergometric test was limited by fatigue or dyspnea in all subjects, exercise duration was used as an effort tolerance index. Echocardiographic indexes of systolic function resulted normal in all subjects. Significant relationships with exercise duration were found for several indexes of left ventricular filling (A peak: r = -.743, p < .0001; A/E ratio: r = -.606, p < .005; early filling fraction: r = .639, p < .001). Exercise time was also significantly related to casual blood pressure, both systolic and diastolic. The relationships between transmitral blood flow and exercise capacity seem to indicate that an impairment of ventricular relaxation (as indicated by the progressive increase of atrial contribution) is associated with a decreased exercise tolerance, possibly because a progressively lower activation of Frank-Starling mechanism. Diastolic function thus seems to be able to affect exercise tolerance even in subjects with normal systolic function and blood pressure ranging from normal to severely elevated values.     

Pulsed Doppler evaluation of left ventricular filling in subjects with pathologic and physiologic third heart sound

Haemodynamic studies suggest that the rapid deceleration of left ventricular inflow at the end of early diastole may play an important role in the genesis of the third heart sound (S3). To confirm this hypothesis noninvasively, pulsed Doppler of transmitral flow was used. Mitral flow velocity wave was recorded in 20 post-infarction patients with audible S3 (Group 1), in 20 young healthy individuals with physiologic S3 (Group II), in 20 postinfarction patients without S3 (Group III) and in 20 normal adults (Group IV). Peak flow velocity in early diastole (Ev), peak flow velocity during atrial systole (Av), the Ev/Av ratio, the deceleration of early diastolic flow (EF slope), the ratio of the time velocity integral of early diastole to the total time velocity integral (TVle/TVlt) and the isovolumic relaxation time (IVRT) were measured from Doppler recordings. The time relation between S3, the mitral valve motion on M-mode tracing, and the mitral flow velocity wave were analysed comparing the intervals from the second sound to Ev (A2-Ev), to the E point of mitral valve motion (A2-Em) and to the S3 (A2-S3). In groups I and II Ev/Av ratio was higher (respectively 4.4 +/- 2.2 and 2.8 +/- 1.1) than in group III (0.8 +/- 0.4) and IV (1.3 +/- 0.3). Similar results were found for the TVle/TVlt ratio. In both groups with S3, EF slope was significantly steeper (respectively 9 +/- 1.8 and 7.5 +/- 1.1 m s) than in normal adults (4.4 +/- 1.1 m s) and patients without S3 (3.6 +/- 1.1 m s).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of heart rate on left ventricular diastolic transmitral flow velocity patterns assessed by Doppler echocardiography in normal subjects

Although a number of factors, including age and ventricular loading, are known to influence the pattern of left ventricular (LV) filling as depicted by Doppler echocardiographic transmitral flow velocities, few and conflicting data are available regarding the influence of heart rate (HR). Therefore, 20 volunteers (mean age 30 years) were evaluated with pulsed-wave Doppler echocardiography, performed with the sample volume placed at the mitral anulus level in the apical 4-chamber projection. Transmitral flow measurements comprised peak and integrated early passive (E) and late atrial (A) filling velocities and the slope of velocity decline from peak E filling. Measurements were recorded during baseline (sinus rhythm, mean 70 beats/min) and during transesophageal atrial pacing (mean 88 beats/min). LV end-diastolic dimension, mean arterial pressure and PR interval (corrected for pacing-induced delay in interatrial conduction time) were unchanged during pacing versus baseline measurements. Peak and integrated E filling velocities averaged 0.59 +/- 0.09 m/s and 6 +/- 1 cm, respectively, at baseline and were not significantly greater at the higher HR. In contrast, baseline peak and integrated A velocities averaged 0.37 +/- 0.06 m/s and 2.3 +/- 0.7 cm, respectively, but were significantly greater at the higher HR (0.5 +/- 0.07 m/s and 3.2 +/- 1.1 cm, respectively [p less than 0.003 vs baseline for each]). Further analysis of a subgroup of 9 subjects for whom Doppler measurements were available at 3 HRs (sinus 70; pacing 80 and 90) yielded strong evidence for a linear relation between HR and peak A velocity (A = 0.008 HR - 0.21, with p less than 0.0001 for significance of the linear trend).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of aging on left ventricular diastolic filling in normal subjects

To determine the effect of aging on left ventricular filling, mitral valve flow was evaluated with real-time (color flow) and conventional pulsed Doppler echocardiography in 32 subjects, aged 24 to 68 years, who had no evidence of cardiovascular disease. The diameter of mitral valve flow was measured in early and late diastole in the apical 4-chamber view. Transmitral velocities were measured in early and late diastole with pulsed Doppler echocardiography. The early flow diameter was significantly smaller in patients older than 50 than in those aged 20 to 29 years (p less than 0.05), while atrial flow diameter was significantly larger in patients older than 50 than in those aged 20 to 29 years (p less than 0.05). The ratio of early flow diameter to atrial flow diameter was 1.85 +/- 0.33 in patients 20 to 29 years old and 1.17 +/- 0.28 in those older than 50 (p less than 0.001). The ratio of early to atrial diastolic velocities was 1.98 +/- 0.53 in the younger patients and 1.07 +/- 0.41 in those older than 50 years (p less than 0.001). The ratio of early flow diameter to atrial flow diameter decreased significantly with aging, and this decrease had a negative correlation with aging (r = -0.64). Qualitatively, in these normal subjects, early diastolic flow filled the ventricle centrally, while with atrial contraction, flow entered the ventricle toward the posterolateral wall and was associated with flow moving toward the aortic valve along the ventricular septum.(ABSTRACT TRUNCATED AT 250 WORDS)     

Myocardial mechanics in hyperthyroidism: importance of left ventricular loading conditions, heart rate and contractile state

Hyperthyroidism has been reported to affect all of the major determinants of left ventricular performance in a manner that would augment ventricular shortening characteristics. The hypothesis tested in this study is that reduced afterload in conjunction with increased preload and heart rate, rather than augmented contractility, accounts for much of the increase in left ventricular performance noted previously in these patients. To investigate this hypothesis, 11 hyperthyroid patients were evaluated serially over 4 +/- 2 months. With therapy, serum total thyroxin (T4) decreased significantly (p less than 0.001). Ventricular hemodynamics were assessed by two-dimensional targeted M-mode echocardiograms and calibrated carotid pulse tracings. Ventricular preload was estimated by end-diastolic dimension, whereas afterload was measured as end-systolic wall stress. Overall left ventricular performance was quantitated by the extent and velocity of shortening, whereas myocardial work was assessed by ventricular systolic stress-length relations. With therapy, overall left ventricular performance declined (p less than 0.01). This change was associated with no change in end-diastolic dimension or end-systolic wall stress, and a 24% fall in heart rate (p less than 0.01). This latter finding has been shown previously to have no significant effect on left ventricular contractile state over the range of heart rates encountered in this study. In all cases, the end-systolic stress/rate-corrected shortening velocity relation fell with attainment of normal thyroid status, characteristic of a decline in contractility. There was a strong positive correlation between left ventricular contractility and serum thyroid hormone level (r = 0.83). In addition, ventricular minute work declined with therapy (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Adjustment for the influence of age and heart rate on Doppler measurements of left ventricular filling

Objective—To determine the normal range of pulsed Doppler measurements of left ventricular filling adjusted for age and heart rate.

Design—Multiple regression was used to measure the effects of age and heart rate on pulsed Doppler indices of left ventricular filling in normal subjects. These regression equations were used to calculate a predicted normal value and 95% confidence interval (95% CI) for any subject from his age and heart rate.

Participants—61 subjects with no evidence of cardiovascular disease, aged 20 to 90 years, with a resting heart rate of 47–89 beats/min.

Results—The effect of a 10 year increase in age was peak atrial filling velocity +15% (95% CI 12·0% to 18·5%); peak early filling velocity −3·2% (−6·0% to 0%); isovolumic relaxation time +6·2% (3·9% to 8·4%); acceleration time −3·8% (−6·0% to −1·5%); deceleration time +7·9% (5·1% to 10·8%). The effect of a 10 beat/min increase in heart rate was: peak atrial filling velocity +5·5% (1·2% to 10·1%); peak early filling velocity −4·0% (−8·1% to 2·0%); isovolumic relaxation time −2·5% (−4·6% to 0·6%); acceleration time −3·1% (−6·4% to 0·4%); decleration time −1·8% (−4·0% to 3·8%).

Conclusion—For any individual, comparison of the predicted normal measurement and 95% CI with the observed measurement allows an assessment of the effects of disease on left ventricular filling that is independent of age and heart rate.

     

Adjustment for the influence of age and heart rate on Doppler measurements of left ventricular filling

Objective—To determine the normal range of pulsed Doppler measurements of left ventricular filling adjusted for age and heart rate.Design—Multiple regression was used to measure the effects of age and heart rate on pulsed Doppler indices of left ventricular filling in normal subjects. These regression equations were used to calculate a predicted normal value and 95% confidence interval (95% CI) for any subject from his age and heart rate.Participants—61 subjects with no evidence of cardiovascular disease, aged 20 to 90 years, with a resting heart rate of 47–89 beats/min.Results—The effect of a 10 year increase in age was peak atrial filling velocity +15% (95% CI 12·0% to 18·5%); peak early filling velocity −3·2% (−6·0% to 0%); isovolumic relaxation time +6·2% (3·9% to 8·4%); acceleration time −3·8% (−6·0% to −1·5%); deceleration time +7·9% (5·1% to 10·8%). The effect of a 10 beat/min increase in heart rate was: peak atrial filling velocity +5·5% (1·2% to 10·1%); peak early filling velocity −4·0% (−8·1% to 2·0%); isovolumic relaxation time −2·5% (−4·6% to 0·6%); acceleration time −3·1% (−6·4% to 0·4%); decleration time −1·8% (−4·0% to 3·8%).Conclusion—For any individual, comparison of the predicted normal measurement and 95% CI with the observed measurement allows an assessment of the effects of disease on left ventricular filling that is independent of age and heart rate.     

Doppler assessment of right ventricular filling in a normal population. Comparison with left ventricular filling dynamics

To examine whether alterations in right ventricular filling dynamics occur with increasing age and to compare right and left ventricular filling in normal subjects, pulsed Doppler echocardiographic studies were performed at the tricuspid and mitral anuli in 50 normal volunteers (23 males and 27 females) with an age range of 5-66 years. An age-related decrease in peak early filling velocity, increase in peak late velocity, and augmentation in the late/early ratio of peak velocities at the tricuspid anulus were observed (r = -0.68, 0.63, and 0.84, respectively). Significant correlations were also found between age and first third, first half, and atrial filling fractions (r = -0.60, -0.72, and 0.69, respectively). Weaker relations were observed between heart rate and Doppler-derived diastolic parameters (r = 0.18-0.54). Right ventricular filling indexes related significantly to those of the left ventricle (r = 0.58-0.88), the best being for the late/early ratio of peak velocities. With inspiration, an increase in early and late right ventricular filling occurred, whereas a reduction in filling occurred in the left ventricle. Thus, careful consideration for age, heart rate, and respiration is necessary in examining the effect of disease states or therapeutics on the filling dynamics of either the right or left ventricle.